1. Field of the Invention
The invention relates generally to double-faced display devices, and more particularly to double-faced field emission display devices.
2. Prior Art
A field emission display device has been widely used in computers, mobile communications and consumer electronics. Conventionally, the field emission display device comprises a fluorescent screen and an electron emission structure. The fluorescent screen comprises an anode plate formed thereat, and the electron emission structure comprises a cathode plate formed thereat. In use, when an emitting voltage is applied between the anode plate and the cathode plate, electrons are emitted from the cathode plate and bombard the fluorescent screen, whereby visible light is produced and an image is displayed on the fluorescent screen. The field emission display device only displays a single image at one surface thereof.
In certain applications, a field emission display device is required to simultaneously display the same image at two opposite surfaces thereof. In order to meet such needs, it is commonplace to simply combine a pair of field emission display devices and thus form a two-sided field emission display device assembly. In the field emission display device assembly, two driving systems are needed. Furthermore, a structure of the field emission display device assembly is complicated. Thus, the field emission display device assembly is bulky and costly.
In order to solve the above-mentioned problems, a so-called double-faced field emission display device has been developed. Referring to FIG. 4, the double-faced field emission display device comprises a pair of parallel fluorescent screens 3, and a cathode plate located between the fluorescent screens 3. Each fluorescent screen 3 acts as an anode plate, and is electrically connected with an anode lead 1. The cathode plate is electrically with a cathode lead 5, and has a plurality of silicon point arrays 2 formed at opposite surfaces thereof. In use, when an emitting voltage is applied between each fluorescent screen 3 and the cathode plate, the silicon point arrays 2 emit electrons. The electrons bombard the fluorescent screen 3, whereby an image is displayed on the fluorescent screen 3.
However, a distance between the cathode plate and each fluorescent screen 3 is in a range from 2 to 30 micrometers. Thus, the emitting voltage needs to be relatively high. In addition, the emission of the electrons cannot be controlled very accurately. Furthermore, a pair of emitting spaces is defined between the cathode plate and the fluorescent screens 3 respectively, with the emitting spaces being independent of each other. This means that when the double-faced field emission display device is manufactured, the emitting spaces must be separately evacuated. Furthermore, the images displayed at the two fluorescent layers 3 may not be identical.
A double-faced field emission display device which overcomes the above-mentioned problems is desired.